1. Field of the Invention
The present invention relates to a short circuit preventing film for preventing short-circuiting between electrodes which is suitable for use in a liquid crystal electro-optical device. The invention also relates to a manufacturing method of such a film.
2. Description of the Related Art
In recent years, liquid crystal electro-optical devices have been investigated actively. A liquid crystal electro-optical device is constructed such that a pair of substrates are facing with each other, electrodes or electrodes and switching elements such as thin-film transistors are provided inside the respective substrates, and a space between the substrates are filled with a liquid crystal material. The liquid crystal electro-optical device may be used as display or some other function utilizing an optical response characteristic of the liquid crystal material.
Each of the substrates of the liquid crystal electro-optical device that face each other has an electrode on its surface, and the interval between those electrodes is very small; for instance, 5-8 .mu.m in TN (twisted nematic) type devices and 1-4 .mu.m (typically, 1.5 .mu.m) in devices using a ferroelectric liquid crystal. Therefore, when a very small impurity, dust, etc. exists between the electrodes, very serious problems occur. More specifically, short-circuit between the electrodes produces by existence of the impurity or the like. Therefore, a display failure, a defective point in a display, or other problems occur.
Conventionally, to solve this problem, a silicon oxide (SiO.sub.2) film of about 1,000 .ANG. in thickness is formed as a short circuit preventing film. However, pinholes are likely to produced in this film. The breakdown voltage of SiO.sub.2 film having 1,000 .ANG. in thickness is low, in a range of 5 to 20 V and changes largely. Therefore, this film does not have sufficient characteristics for short circuit prevention. In addition, since the relative dielectric constant of this film is as low as 2 to 5, a loss of an electric field to be applied to the liquid crystal material produces, deteriorating characteristics of the device, such as the contrast.